Skynet

Skynet 5A is the first of the 'new generation' of British Military satellites. It was launched on March 11, 2007 by Arianne-Space. Skynet 5A was initially placed at about 177W where it underwent testing by the USAF Satellite Control Facility. It was then relocated to its operational slot at 1W where it will be commanded by RAF Oakhanger.S-Band TT&C has been observed on 2227.500MHz. Skynet 5A has 9 UHF transponders and 15 SHF transponders operating at X-Band. The X-Band signals wobble slightly, it is presumed that this is due to the oscillator settling down, or thermal effects. Its estimated that SN5A has about a 20dB horn antenna for Earth coverage downlink on X-Band. It is also quite possible that there is a steer able X-Band antenna of about 60cms to 1m diameter. The UHF helical antennas are probably about 8 turns to give Earth coverage. There may also be Ka band downlinks but this is yet to be confirmed.

UHF Satcom Frequencies

Downlink Freq Bandwidth Notes Transponder spectrum plot
245.800 MHz 25 KHz
249.480 MHz 10 KHz 2 tone IMD testing 17:08 30/3/2007

249.530 MHz 10 KHz GMSK mil comms active
249.850 MHz 10 KHz
250.130 MHz 10 KHz
250.200 MHz 10 KHz
257.700 MHz 25 KHz
261.280 MHz 25 KHz Originally on 261.200MHz

S-Band TT&C frequencies

Downlink Freq Notes Transponder spectrum plot
2227.500 MHz Coherent TPX - carrier seen drifting in and out of lock.

SHF-SatCom frequencies

Downlink Freq Bandwidth Notes Transponder spectrum plot
7261.000 22 MHz Active with a few PSK signals
7287.750 22 MHz
7314.500 22 MHz
7340.250 20 MHz
7365.000 20 MHz
7401.000 36 MHz
7447.000 40 MHz
7494.000 MHz Tracking beacon or TT&C (+-20KHz data) - probably QPSK
7494.045 MHz PSK with cyclic data, possible TT&C
7488.000 34 MHz Regenerative beacon and TT&C etc
7529.000 40 MHz
7577.000 40 MHz
7615.000 20 MHz
7640.000 20 MHz
7666.000 22 MHz
7689.000 22 MHz
7715.000 20 MHz
7740.000 20 MHz

Skynet 5B is the second of the 'new generation' of British Military satellites. It was launched on November 14th, 2007 by Arianne-Space. Skynet 5B was initially placed at 6E where it underwent in orbit testing. It was then relocated to its operational slot at 53E where it will be commanded by RAF Oakhanger.

UHF-SatCom frequencies

Downlink Freq Bandwidth Notes Transponder spectrum plot

245.200 MHz

35KHz
249.4395 MHz 8KHz
249.460 MHz 8KHz
249.4995 MHz 8KHz
249.5095 MHz 8KHz
250.1795 MHz 8KHz
253.980 MHz 35KHz

QRM!!

257.900 MHz 35KHz 2.5Kbps BPSK
261.100 MHz 35KHz

S-Band TT&C frequencies

Downlink Freq Notes Transponder spectrum plot
2227.500 MHz Coherent TPX - carrier seen drifting in and out of lock.

SHF-SatCom frequencies

Downlink Freq Bandwidth Notes Transponder spectrum plot
7261.000 22 MHz
7287.750 22 MHz
7314.500 22 MHz
7340.250 20 MHz
7365.000 20 MHz
7401.000 36 MHz
7447.000 40 MHz Single PSK cf=7427.5MHz
7495.800 MHz Tracking beacon or TT&C (+-20KHz data) - probably QPSK
7488.000 34 MHz
7529.000 40 MHz
7577.000 40 MHz
7615.000 20 MHz
7640.000 20 MHz
7666.000 22 MHz
7689.000 22 MHz
7715.000 20 MHz
7740.000 20 MHz

Skynet 5C is the third of the 'new generation' of British Military communications satellites. It was launched on June the 12th, 2008 by Arianne-Space from Kourou. Skynet 5C (#33055) is currently parked at its geostationary slot of 17.88 degrees West. Currently, the X-Band TT&C and S-Band beacons are active, withX-Band transponder testing underway. The X-Band TT&C beacon was activated around 11:30 BST on the 26th June 2008.

UHF-SatCom frequencies

Downlink Freq Bandwidth Notes Transponder spectrum plot

245.900

38KHz

249.500

8KHz

249.550

8KHz

249.880

8KHz

249.900

8KHz

250.100

8KHz

254.730

38KHz
256.5905

(Note: This tpx has moved to 256.600)

38KHz

261.100

38KHz

S-Band TT&C frequencies

Downlink Freq Notes Beacon spectrum plot
2252.486MHz

SHF downlink frequencies (monitored off air)

Downlink Freq Bandwidth Notes Downlink spectrum plot
7249 to 7273 24MHz spot beam ? 7261.000 tpx centre - not confirmed with tpx noise tests
7275.75 to 7299.75 24MHz steerable beam ? 7287.750 tpx centre
7302.5 to 7326.5 24MHz steerable beam ? 7314.500 tpx centre
7328.25 to 7352.25 24MHz steerable beam ? 7340.250 tpx centre
7353 to 7377 24MHz steerable beam ? 7365.000 tpx centre
7378 to 7422 44MHz
7425 to 7469 44MHz 7447.000 tpx centre - not confirmed with tpx noise tests
7471 to 7505

From L to R:

7491.74904 PSK

7492.200 CW

7492.24404 PSK

7492.55904 PSK

34MHz TT&C beacons

2 narrow band telemetry downlinks running at 19.2Kbps BPSK / DSSS

earth coverage horn or low gain antenna

7505 to 7553 48MHz steerable beam ? 7529.000 tpx centre
7554 to 7600 48MHz
7604 to 7628 24MHz spot beam ? 7616.000 tpx centre
7628 to 7652 24MHz 7640.000 tpx centre - not confirmed with tpx noise tests
7655 to 7677 22MHz 7666.000 tpx centre - not confirmed with tpx noise tests
7677 to 7701 24MHz 7689.000 tpx centre - not confirmed with tpx noise tests
7703 to 7727 24MHz spot beam ? 7715.000 tpx centre
7728 to 7752 24MHz 7740.000 tpx centre - not confirmed with tpx noise tests

sn5ctpxmv1 sn5ctpxmv2

The pictures above show two transponder moves during the commissioning of Skynet 5C.

Skynet 5D is the forth and final of the 'new generation' of British Military communications satellites. It was launched on the 19th December 2012 at 21:49 UTC by Arianne-Space from Kourou. Skynet 5D (#39034) is currently parked at its geostationary slot of 25 degrees East. Currently, UHF, X-Band transponders, X-Band TT&C and S-Band beacons are active. The X-Band TT&C beacon was activated around the 6th January 2013.

SHF downlink frequencies (monitored off air)

Downlink Freq Bandwidth Notes Downlink spectrum plot
7275.000
7314.500
7320.000
7365.000
7401.000
7447.000

From L to R:

7491.74904 PSK

7492.200 CW

7492.24404 PSK

7492.55904 PSK

34MHz TT&C beacons

2 narrow band telemetry downlinks running at 19.2Kbps BPSK / DSSS

earth coverage horn or low gain antenna

7529.000
7550.000
7589.500
7730.000

On the 8th January 2013, Skynet 5D UHF / X-Band tests were underway, with a test of the onboard UHF receiver. The output of the onboard receiver was looped to an X-Band downlink centred at 7314.500MHz, resulting in approximately a 30MHz wide lump of RF being down linked. The FFT below shows the 30MHz wide downlink - you can click on it for the full resolution version. Signals included most of the Braziallian pirates, Sicral DAMA uplinks, UHF air to air comms, including UAV coordination frequencies, Link 11 / TADIL comms, ATIS from Chang-Mai airport, Russian terrestrial phone trunks, and hundreds more signals.

sn5dx